![]() I don’t know what the value will be, but N is ideally 1 from what I understand. So I chose the following values:Īssuming an open circuit voltage of 0.8V and a short circuit current of 0.5A, I determined the value of reverse saturation current as As far as I could see, the diode saturation current and ideality factor (or emission coefficient N) are the only parameters that would affect the diode forward characteristics. So I decided to model a diode which would approximate the solar cell diode. In fact, the capacitor voltage doesn’t even start from 0V at t = 0s.Īfter some experiments, I’ve found that the level to which the capacitor voltage drops during discharge is dependent on the diode model I’ve chosen. That is, the capacitor does not discharge completely to zero. However, the simulation shows that the capacitor charges and discharges between two fixed DC levels. I’ve used the simple equivalent circuit consisting of a current source, diode and series and shunt resistances to model the solar cell. However, the simulation yields unexpected results. Because 7404 inverter output is between 0 and 1 V, I’ve used a non-inverting amplifier to change this to 0 and 5V, so that MOSFET switching action takes place. I’m using an inverter between the two switches so that the switching takes place in an alternating fashion. I’ve created a circuit based on this idea and simulated it using LTSpice IV. The next switch is used to discharge the capacitor through a resistor so that it can be used for another measurement. The first switch charges the capacitor from 0 V to the open circuit voltage of the solar cell. An MCU uses PWM to control two MOS switches. I’ve incorporated a switching arrangement in the design so that the capacitor may be charged and discharged at times controlled by the user. I’m hoping to use the same technique to measure the IV characteristics of a single solar cell. This method is used to characterize large PV modules. The values of the current and voltage sensors during the time the capacitor is being charged directly corresponds to the required set of values for IV characteristics. A current sensor measures the current flowing to the capacitor and the voltage across the capacitor is measured by a voltage sensor. The idea is to charge a capacitor with the solar cell. I’m designing a circuit to measure the IV characteristics of an illuminated solar cell.
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